1. Field of the Invention
This invention relates generally to mechanically stabilized embankment systems, and more particularly to a mechanically stabilized embankment system that includes a wall facing element connected to elongate soil reinforcement elements each having a plurality of semi-extensible bent segments spaced along the length of the soil reinforcement element.
2. Description of Related Art
The prior art teaches various forms of mechanically stabilized embankment systems for stabilizing earthen embankments. These systems include a wall facing element connected to elongate soil reinforcement elements that extend into the earthen embankment. The prior art elongate soil reinforcement elements fall into three categories: (1) extensible reinforcements made of plastic or other material that stretch under pressure, (2) non-extensible rods made of steel or the like that have a deformable region in a proximal end of the rod adjacent the wall facing element, to accommodate some relative movement between the rods and the wall facing element (e.g., in the event of an earthquake), and (3) non-extensible rods that are bent at a distal end for the purpose of anchoring the rod in the earthen embankment.
In the first category, extensible plastic reinforcements are effective in accommodating movement of the earthen embankment along the entire length of the reinforcements. The disadvantage of such systems is that the reinforcements are completely extensible, and there is nothing to limit the stretching of the reinforcements. Over-stretching the reinforcements weakens them and may cause movement of the face and failure of the system.
In the second category, non-extensible steel rods with deformable sections adjacent the wall facing element are useful in mitigating damage from earthquakes and some movement of the rods immediately adjacent the wall facing element, while still maintain support for the facing wall. Munster, U.S. Pat. No. 1,762,343, for example, teaches a system wherein the anchor elements are slidably attached to the retaining wall. Hilfiker, U.S. Pat. No. 4,343,572, teaches a system wherein the anchor elements include deformable sections adjacent the facing wall, so that the anchor element may move with the embankment in the event of an earthquake or other form of movement adjacent the facing wall.
While the steel rods of this second category function to deform under the stresses adjacent the wall, they are not able to accommodate stresses placed upon the rods inside the earthen embankment. Since the rods are not extensible within the earthen embankment, they must be made with sufficiently steel to prevent failure within the earthen embankment, this driving up the costs of the system
The third category is of non-extensible steel rods having a bent “swiggle” anchor at the distal end opposite the wall. The “swiggle” anchor functions to anchor the rods more firmly in the earthen embankment. An example of such a construction is shown in Hilfiker, U.S. Pat. No. 4,834,584. However, this form of “swiggle” anchor is unable to accommodate movement within the earthen structure.
Other prior art patents of interest include Hilfiker, U.S. Pat. No. 7,073,983, Hilfiker, U.S. Pat. No. 4,929,125, Hilfiker, U.S. Pat. No. 4,993,879. All of the above-described references are hereby incorporated by reference in full.
The prior art provides extensible plastic reinforcements, and non-extensible steel rods that include deformable, bent portions at either the proximal or distal ends; however, the prior art does not teach semi-extensible elongate soil reinforcement elements that include bent sections through the middle of the elongate soil reinforcement elements, that are partially extensible. Such semi-extensible elements provide accommodation to movement within the earthen embankment, as described below, without weakening the elongate soil reinforcement elements. The present invention fulfills these needs and provides further related advantages as described in the following summary.